The invention is based on a bolt pushing tool with which steel bolts can be inserted in hard material, e.g. concrete for fixing articles. The known bolt pushing tools make use of a propellant charge for producing the feeding or advance force, said charge being ignited and as a result of the explosive gases released a piston is driven. The piston then acts on the head of the bolt and pushes it out of the tool.
Numerous tools exist with which clips or nails are driven in. Such tools are known in the form of compressed air tackers or electrical tackers. However, these are not able to produce the characteristic force for bolt pushing tools.
The problem of the invention is to further improve a device for producing an abrupt or sudden feed motion with respect to the safety of handling. The device must e.g. be usable as a drive for a bolt pushing tool.
For solving this problem the invention proposes a device having the features of claim 1. Further developments of the invention form the subject matter of dependent claims, whose wording like that of the abstract is, by reference, made into part of the content of the description.
Whereas in the case of the known bolt pushing tools working always takes place with explosions, the device proposed by the invention can be operated with a motor drive, which has a lower safety risk. In addition, it is no longer necessary for the user to carry with him and store propellant charge magazines. The drive can e.g. be an electric motor, so that the tool can be operated and handled in the same way as a conventional portable drilling machine. The energy can be supplied by a battery. According to the invention the tool uses the motor drive in order to relatively slowly tension the striker spring. The completely tensioned spring is able to produce an adequately powerful feed or advance in order to e.g. drive a bolt with the same action into the substrate as in the case of the existing explosion-operated tools.
The feed device, which transfers the force of the relaxing spring, can e.g. have a push rod. This push rod can be guided in a corresponding guide and means can be provided in order to decelerate the end of the movement of the push rod if it has excessive energy.
According to a further development of the invention, the device also has a return mechanism for sliding back the feed device from the impact position into the starting position after performing the impact process. This ensures that the device automatically and rapidly returns to its starting position, so that it can be continuously used by a user. As the sliding back of the feed device can be carried out more slowly and with reduced force, the return mechanism can also be operated by the drive. However, it is also possible to give the return mechanism a spring.
It is particularly favourable if the spring element of the spring for performing the impact process and/or the spring element of the return spring is a pressurized gas. In this case the actual spring element has a negligibly low weight, so that the spring can very rapidly relax with a high force.
It can in particular be provided that the feed device has a piston on which the spring element directly acts. For example the push rod can be connected to a piston or constructed in one piece therewith and then the pressurized gas acts directly thereon. The push rod can also comprise several parts.
The piston can in particular be a double-acting piston on which the return spring acts directly.
According to a further development of the invention, the proposed device can have an axial piston guide.
The trigger for triggering the fitting or installation process can in particular have a valve, on whose operation the pressurized gas commences the impact process.
It can in particular be provided that the valve is opened for triggering the impact process.
The invention also proposes constructing the valve in such a way that it has a self-reinforcing opening movement. This ensures that the valve opens very rapidly as soon as it is triggered.
The invention proposes the spring-loading of the valve in the closed position. On triggering the insertion process it is consequently necessary to firstly overcome the spring tension with which the valve is urged into the closed position. This can be used for making the valve opening process jerky.
The trigger for triggering the insertion process can, according to the invention, be designed in such a way that it is triggered by the drive on reaching a specific position, which simplifies the handling of the tool.
It can be provided according to the invention that the striker spring is already pretensioned in the starting position of the feed device.
According to a further development of the invention the drive is constructed in such a way that during its operation, in order to initiate an impact process, the striker spring further tensions directly prior to triggering. Therefore the spring does not constantly have to be under maximum tension.
It is also possible to construct the drive in such a way that following the advance of the feed device the striker spring is temporarily further relaxed to facilitate its sliding back.
According to the invention the drive has a tubular element arranged coaxially to the piston guide and displaceable in the longitudinal direction of said piston guide. This makes the construction of the tool compact. Simultaneously the tubular element is guided on the piston guide.
For the displacement of the tubular element it is possible to place on an external thread of the bolt guide a rotatable nut, which during its use displaces by means of a bearing the tubular element.